1. Field of the Invention
The invention relates to introducer sheaths for catheters used for access to the central venous blood supply of a patient while providing a means for cooling or warming a patient.
2. Description of Related Art
Catheters such as central venous line catheters are typically used in ICU (intensive care unit) patients, for example, in patients who have suffered a stroke or other brain traumatic event, or who need cardiac bypass surgery. The central venous line catheters are typically about 8.5-12 French in diameter and consist of a soft, flexible multi-lumen structure extending 8-12 inches. The catheters are usually introduced using an introducer sheath or a guidewire through the subclavian or jugular veins, and less preferably in the femoral vein of the patient. The subclavian, jugular and femoral veins serve to provide an easy access to the patient""s central blood supply via the central venous system. In this manner general access to the central blood supply is gained, enabling for example delivery of drugs, infusion fluids or nutrition, along with the gathering of patient blood for blood gas analysis and the like. Typically, the catheter""s distal end is lodged in the superior vena cava. The superior vena cava is easier to access from a neck or chest insertion point than the inferior vena cava since the superior vena cava is located above the right atrium. If access is to be gained to the inferior vena cava from the subclavian or jugular veins, the catheter must bypass the entry to the right atrium. Inadvertently lodging a catheter in the right atrium can be fatal. However, lodging a catheter""s heat exchange element in the inferior vena cava can be advantageous because the volume of blood returning through the inferior vena cava is about 66% to 75% of the total blood volume of a patient compared to a blood volume of about 25% to 34% in the superior vena cava.
In many patients, such as ICU patients or head trauma patients, fever is a common occurrence and its onset can exacerbate detrimental effects. Conventional therapies to control fever include treatment with acetaminophen (Tylenol(copyright)), cooling blankets, ice water bladder lavages, and ice baths. All of these approaches to cooling a patient require excessive time to cool the patient. Moreover, prior methods do not provide for precise control of patient cooling. As recognized herein, to optimize the advantage of cooling a patient, it is important to cool the patient relatively quickly in a controlled fashion.
Similarly, a post surgery patient may require active rewarming to prevent shivering. Postoperative shivering increases metabolic rate and potentially may lead to myocardial ischemia among other things. Thus, prevention of postoperative shivering is desirable. The present invention recognizes these problems and provides the solutions discussed below to one or more of them.
The present invention overcomes the deficiencies of the prior art by adapting an introducer sheath with an angling membrane at its distal tip and a mechanism to inflate and deflate the angling membrane. The present introducer sheath is used for positioning a catheter in the inferior vena cava from a chest or neck insertion point. It includes a hollow body defining a proximal end, a distal end positionable in a patient, at least one catheter placement lumen extending therebetween, an angling membrane and an inflation/deflation mechanism. Once the catheter""s heat exchange elements are firmly positioned in the inferior vena cava, the angling membrane can be deflated and the angling introducer sheath removed.
The catheter can be a catheter having an internal circulating fluid as disclosed in U.S. Pat. Nos. 6,126,684 and 5,837,003, incorporated herein by reference, or other similar device. In one embodiment, the catheter is a central venous line catheter which can include heat exchange elements to actively exchange heat with the body of the patient to thereby raise or lower body temperature as required. The catheter is provided with a heat exchange element disposed in heat exchange relationship with the blood of the patient. The heat exchange element houses a circulating fluid therein, with the fluid being automatically cooled or warmed exteriorly of the patient""s body in accordance with a patient temperature feedback scheme.
The access, typically through the subclavian or jugular veins, is to the central blood supply, via the central venous system, and is therefore particularly expedient, permitting efficient cooling or warming of patient body temperature. The term central venous system generally relates to the portion of the venous system which returns blood to the right heart, including the superior and inferior vena cava. The heat exchange relationship between the catheter and the central venous system of the patient can be maintained for a prolonged duration, for example, from about one hour to about twenty-nine days.
The catheter comprises a tubular structure defining a plurality of lumens. At least two of these lumens convey heat exchange fluid to a heat exchange element disposed at a distal, implantable end of the catheter, while the rest of the lumens serve to provide access to the central blood supply of the patient. The heat exchange element is in fluid communication with a temperature control module via a tubing set which conveys the heat exchange fluid between the components. The temperature control unit, comprising a cooling and/or a heating device, operates in conjunction with a temperature controller to heat or cool the heat exchange fluid depending on a sensed temperature of the patient.
The invention thus provides for controlling patient temperature using a neck or chest insertion point to insert a central venous line catheter having a heat exchange element and to position the catheter""s heat exchange elements in the inferior vena cava . The catheter is provided with one or more lumens for providing access to the central blood supply of the patient, and with additional lumens for communicating heat exchange fluid to the heat exchange elements. Heat exchange fluid temperature is controlled through a feedback loop in which patient temperature is sensed and used to control a temperature control unit comprising a heating device and/or a cooling device in heat exchange relationship with the heat exchange fluid. A tubing-set transports the heat exchange fluid between the catheter and the temperature control unit, with a pump serving to circulate the fluid in a closed fluid circuit.